“The whole cascade works perfectly”: Dr. Kekelidze on the creation of the NICA collider in Dubna

— Vladimir Dimitrievich, please tell us how the idea of ​​creating the NICA collider in Dubna came about and what tasks it will have to solve

— High-energy physics studies the microworld and the fundamental laws of nature, which are the same for both the atom and the Universe.

A coherent theory that describes the fundamental forces of nature, with the exception of gravity, is called the Standard Model.

These forces are electromagnetism, the weak interactions that cause nuclear decays, and finally the strong interactions that keep protons and neutrons in nuclei.

The Standard Model describes all these three types of interactions well, but has a number of "white spots" - especially in the description of strong interaction processes, which are the strongest in nature.

• Vladimir Kekelidze

• © Joint Institute for Nuclear Research

In the 2000s, the world scientific community began to search for solutions to the problems of the transition of nuclear matter to various states (phases) - from quarks and gluons to protons and neutrons and vice versa.

The scientists of our institute were also involved in discussions on these issues, and as a result of intensive discussions, it was decided to start such research, for which purpose, on the basis of the existing superconducting accelerator Nuclotron, to create such an installation that would allow finding answers to at least part of the questions posed and, possibly, , to close some "white spots".

This was the beginning of the NICA project, whose name stands for Nuclotron based Ion Collider fAcility (Collider facility based on the Nuclotron).

The building blocks of our universe are quarks and gluons.

Quarks are elementary indivisible particles that make up all matter, and gluons are the forces that bind them, carriers of the strong interaction.

Each proton or neutron (commonly called nucleons) is made up of three valence quarks.

But if we add up their mass, then we get only 2% of the mass of the nucleon, 98% will fall on the energy of interaction between quarks due to gluons.

That is, in fact, you and I consist mainly of gluon energy, which binds quarks.

These are very strong and complex interactions that reach their maximum strength at a distance of the characteristic size of the nucleon when you try to rip a quark out of it.

Conversely, as quarks come closer together, these forces weaken, so that if you bring them close enough, the interaction can be so weakened that the quarks are released.

After the quarks lose their bonds and fly apart, they soon begin to group anew into protons and neutrons or other so-called.

elementary particles.

There are different ways to bring quarks closer: for example, you can accelerate two protons and collide, then the quarks that make up them will also collide if you apply enough energy and aim well.

Or you can compress matter so that the protons and neutrons in the nuclei of atoms penetrate each other and the quarks get so close that they almost cease to interact.

Then we will get the so-called quark-gluon porridge or quark-gluon plasma, which in nature exists only in the depths of neutron stars - there it is formed due to strong gravity, under very high pressure.

• Illustration depicting the events of the Big Bang

• Gettyimages.ru

• © Tobias Roetsch/Future Publishing

By studying the origins and properties of quark-gluon plasma, we could come closer to understanding one of the great unsolved mysteries: how quarks are bound in neutrons and protons by the strongest bond known to science.

The theory does not give a rigorous description of this phenomenon, and experimental data are also insufficient.

You can get such data if you collide the nuclei of atoms, where there are a lot of protons and neutrons - for example, gold or lead.

Theorists predict a certain range of energy needed for this.

It is clear that if it is too large, the protons and neutrons will simply pass through each other and cannot be compressed.

And if the energy is too weak, the experiment will also fail.

— That is, 

— Yes, this is the main task for the solution of which we started this project — to study quark-gluon matter in high-density conditions.

But there is also a second problem.

As is known, the spin of a particle can be conditionally represented as its orbital rotational motion.

Quarks have it, and it is logical to assume that the addition of the spins of the quarks that make up the nucleon could also determine the spin of the nucleon.

But the very first experiments showed that only 30% of the spin of the entire nucleon is explained by quark spins.

And what explains the remaining 70% - the theory does not yet give an exact answer.

To study how the spin of nucleons is arranged is our second task.

To do this, it will be necessary to collide not the nuclei of atoms, but two protons, in which the spin is no longer chaotic, but polarized, aligned.

In this case, it will be possible to understand the logic of spin relationships.

Our second task is to study the spin structure of the nucleon.

Two experimental approaches are usually considered for studying particle collisions.

The first uses a conventional accelerator, from which an accelerated particle is ejected and hits a stationary target.

The second approach uses a collider in which two particles flying towards each other collide.

Each of the approaches has its pros and cons.

In the first case, we, as a rule, cannot register all the reaction products, because some of them get stuck in the target.

But in this case, the researchers have huge statistics, because each projectile hits the target.

In the collider, the process can be compared to two snipers who, at a distance of a kilometer, are trying to hit a bullet with a bullet.

A collision will occur, perhaps, only in every millionth case.

We need to collect many billions of collisions in order to determine the laws of the processes under study with high accuracy.

An important characteristic of each collider is the so-called "luminosity", an indicator of the frequency of particles hitting each other.

• NICA collider under construction

• RT

Now in the world two projects are aimed at solving similar problems, but by different methods.

This is an experiment at the NICA collider and an experiment with a fixed target at the FAIR accelerator, which is being built in Germany with the participation of Russia, by the way.

The two projects complement each other—scientists have always considered them to be mutual extensions.

It's like brothers who worked together until recently.

- Now the interaction is suspended?

- Yes, so far the German side has suspended cooperation, but I hope that it will resume.

They will not be able to work without us, and it will be difficult for us without them, although we will do something, albeit worse.

As mentioned above, the base of the NICA collider is the Nuclotron superconducting synchrotron - it was built in the early 1990s and was modernized in 2010, when it was decided to build the NICA collider.

The Nuclotron is a unique, interesting machine; for the first time in Russia, an accelerator was built on cryogenic superconducting magnets that operate at a temperature close to absolute zero.

The magnets were developed here, at JINR, and that is why they are called "Dubna".

They will build up the magnetic field very quickly and are ideal for operating at energies such as will be used in the NICA collider or in the FAIR accelerator, for which we also produced them.

There are no analogues in the world, so the German partners will not be able to continue their work without our magnets.

— And what does the German side supply for the NICA collider?

 — High-tech semiconductor strip so-called.

top detectors.

We have created alternative detectors that are inferior in performance, but still such equipment will allow us to start research.

The NICA project is a wide range of different installations and a large engineering infrastructure.

Therefore, the whole thing is called the NICA Complex.

It includes the Nuclotron, which can accelerate particles to the required energy.

But in order to achieve a high luminosity of the collider, a high intensity of particles accelerated in the Nuclotron is required, and this requires another ring accelerator, the so-called.

booster, in which particles are preliminarily accelerated to intermediate energies.

The Complex also includes linear accelerators and channels for transporting particles between all accelerators and channels that bring particles to research facilities, three research facilities - one for conducting an experiment with a fixed target (BM@N) and two for experiments at a collider (MPD and SPD) .

To date, the entire cascade of accelerators, with the exception of the collider itself, has been assembled and tested.

The last tests and adjustments took place in January-March of this year - officially they are called "commissioning works No. 3".

Based on their results, I can say that the entire cascade works perfectly.

Now it remains only to make a large ring of the collider and bring particles into it, otherwise the accelerator part of the Complex is ready.

• NICA collider detector under construction

• RT

The first experiment with a fixed target (BM@N) was carried out on a beam of carbon ions extracted from the Nuclotron, which lasted from March 7 to 31.

185 million interactions of carbon with a resting proton target were collected.

This work involves a large international team of scientists from the United States, Israel, France, Germany, Russia - about 250 people in total.

The purpose of the experiment is to study the so-called.

short-range correlations in the nucleus.

— Explain, please, what is it?

 — This is closer to nuclear physics, but the task is also very interesting.

It is known that if a neutron or a proton is separated from the nucleus of an atom, the properties and mass of these individual protons or neutrons will differ from the properties of the nucleons located in the nucleus.

Because in the nucleus they are brought together and strong interactions arise between them, their properties and even mass change.

And here, too, there are many "white spots".

The phenomenon, which is called short-range correlation, is as follows: with a probability of about 20%, there will always be a pair of proton and neutron in the nucleus, which randomly approach each other so strongly that they begin to experience a strong repulsion, fly apart and receive energy, a noticeable impulse of expansion, although in general the whole pair has very little momentum.

The study of this phenomenon will help to understand the mechanisms of strong bonds in the nucleus,

In previous experiments, an accelerated proton was hit against a carbon nucleus in order to knock out such a pair from it.

Then, by reverse calculations, you can find out how the whole process proceeded.

However, this approach has disadvantages: in order to describe the entire kinematics, it is necessary to calculate it for all reaction products, including the fragment of the nucleus from which we knock out a pair of nucleons.

But in this case, the core will receive a weak return and the fragment will not be able to fly out of the target, it will not have enough energy for this.

It is possible to register only the ejected pair and the proton that was hit on this nucleus - accordingly, it will not be possible to restore the entire kinematics of the reaction.

For the first time, it was proposed to do the opposite - to hit the nucleus on a stationary proton.

In this case, all collision products fly forward, including the remains of the nucleus, and will be registered, you can see the whole picture.

Liquid hydrogen was used as a target for accelerated carbon nuclei.  

Registered 185 million interactions is a good statistic.

It is expected that about 100 events with the full kinematics of short-range correlations, or Short-range correlation (SRC), will be identified from this array of preliminary data.

This is very interesting, because so far no one in the world has conducted experiments in the system of reverse kinetics - when a proton is hit with a nucleus.

This idea became a scientific event in itself and received recognition - it was published in the prestigious scientific journal Physics Nature.

• Scheme of the NICA Complex

• © nica.jinr.ru

- The international team of scientists that conducted these experiments is still working?

— Of course, especially since data processing is usually carried out remotely, in a unified computer environment.

Scientists hold regular meetings and share their results.

So already this year we are waiting for several publications on the results of this experiment.

And in September, a session of work is planned already under the main program.

We are talking about the study of quark-gluon plasma in an experiment with a fixed target (BM@N) using heavy ion beams (Xe) extracted from the Nuclotron.

As for the main ring of the collider, the building to accommodate it has already been built by 98%, it remains to install and launch the engineering infrastructure in it: cooling, heating, air conditioning systems, etc. This will take about six months.

Of course, it will take time for commissioning.

Most likely, we will be able to start experiments on colliding beams at the end of next year.

- Will the current situation with the break in international scientific and technical ties affect the course of work?

 - Yes, it does.

Today, no country fully owns the technology for creating such complex installations as a collider - this is always the result of international cooperation.

It is impossible to completely replace imported equipment, almost 70 countries worked on our project, with manufacturers from which we had contracts.

Now these deliveries are partially “stuck” - something is still to be produced, and some equipment has already been produced, but there are difficulties with its delivery and payment.

Suppliers do not refuse to transfer this equipment to us, it is made specifically for our installations, but we have to look for new delivery schemes and ways to transfer funds.

Solutions are being sought on both sides, and I hope that together we will overcome these difficulties.

• RIA News

• © Vitaly Belousov

- If we return to the tasks that the NICA

collider will have to solve

- According to the generally accepted theory, it all started with the Big Bang, in which quarks and gluons were born.

It was a clot of colossal energy, but there was no matter familiar to us in it - because matter and antimatter were in complete balance.

By itself, a quark can only exist for a moment, it always “picks up” an antiquark and forms a meson, or combines with two other quarks and forms a nucleon.

This is how the Universe was formed, but there was another process that led to an imbalance between matter and antimatter - now there is practically no antimatter in its pure form.

And this mystery has not yet been solved.

But we will study quarks not in their original state, immediately after the Big Bang, but in the state in which they found themselves in the depths of neutron stars.

This is already about hundreds of millions of years since the beginning of the universe.

Is there any application for this research?

 — No, the collider is an installation for conducting only fundamental research.

Let me remind you that Faraday discovered electromagnetic induction, not thinking about the practical application of his discovery, he was engaged in fundamental science.

However, thanks to him, we use electricity today.

Fundamental science deals with the knowledge of the world around us, and the knowledge gained sooner or later gives a new impetus to human civilization.

But when and how this will happen, no one can predict.

However, such a large project as the NICA Complex allows solving practical problems as well.

Firstly, the creation of such installations always requires the most advanced technologies - we set new challenges for the industry.

And in the process of solving them, innovations are already emerging, we indirectly contribute to this.

In addition, beams can be extracted from the accelerators that are part of the NICA Complex (except for the collider) to solve many applied problems.

First, the effect of ionizing radiation on biological objects is studied.

We are conducting experiments with ions, which are very difficult to defend against in outer space and which cause very great destruction in living organisms.

Work is also underway to develop radiation-resistant electronics for space and nuclear power.

There is another interesting direction - attempts are being made to reduce the radioactivity of nuclear waste by irradiating them with various particles - protons or ions.

This is called "transmutation".

We are talking about the neutralization of nuclear waste, but so far it is not clear whether it will be possible to develop the necessary technology.

However, work in this direction still needs to be done.